Re: [PATCH v8 3/9] KVM: arm64: Move hyp_symbol_addr to fix dependency

From: Amit Daniel Kachhap
Date: Sun Apr 07 2019 - 23:42:41 EST


Hi,

On 4/5/19 4:32 PM, Dave Martin wrote:
On Tue, Apr 02, 2019 at 07:57:11AM +0530, Amit Daniel Kachhap wrote:
Currently hyp_symbol_addr is placed in kvm_mmu.h which is mostly
used by __hyp_this_cpu_ptr in kvm_asm.h but it cannot include
kvm_mmu.h directly as kvm_mmu.h uses kvm_ksym_ref which is
defined inside kvm_asm.h. Hence, hyp_symbol_addr is moved inside
kvm_asm.h to fix this dependency on each other.

Also, hyp_symbol_addr corresponding counterpart, kvm_ksym_ref,
is already in kvm_asm.h, making it more sensible to move
kvm_symbol_addr to the same file.

Suggested by: James Morse <james.morse@xxxxxxx>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@xxxxxxx>
Reviewed-by: Julien Thierry <julien.thierry@xxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Cc: Christoffer Dall <christoffer.dall@xxxxxxx>
Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
---

Changes since v7:
* Slight change in commit message [Julien Thierry].

arch/arm64/include/asm/kvm_asm.h | 20 ++++++++++++++++++++
arch/arm64/include/asm/kvm_mmu.h | 20 --------------------
2 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index f5b79e9..57a07e8 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -80,6 +80,26 @@ extern void __vgic_v3_init_lrs(void);
extern u32 __kvm_get_mdcr_el2(void);
+/*
+ * Obtain the PC-relative address of a kernel symbol
+ * s: symbol
+ *
+ * The goal of this macro is to return a symbol's address based on a
+ * PC-relative computation, as opposed to a loading the VA from a
+ * constant pool or something similar. This works well for HYP, as an
+ * absolute VA is guaranteed to be wrong. Only use this if trying to
+ * obtain the address of a symbol (i.e. not something you obtained by
+ * following a pointer).
+ */
+#define hyp_symbol_addr(s) \
+ ({ \
+ typeof(s) *addr; \
+ asm("adrp %0, %1\n" \
+ "add %0, %0, :lo12:%1\n" \
+ : "=r" (addr) : "S" (&s)); \
+ addr; \
+ })
+

Do we need to include <asm/kvm_asm.h> in vgic-v2-cpuif-proxy.c now?
Yes asm/kvm_asm.h should be included now.

Otherwise,

Reviewed-by: Dave Martin <Dave.Martin@xxxxxxx>
Thanks,
Amit D